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This forum exists for the purposes for discussing service monitors (This includes but is not limited to Motorola, HP, Aeroflex, GD, etc). Additional topics allowed include test procedures, interpretation of test results, where to find information about specific tests, antenna VSWR, return loss testing, duplexer and filter alignment, etc.

I am in the process of purchasing a service monitor / test set. Right now I am in the position to buy either a Motorola R2600A with TG from a local radio service tech (no calibration or any other data on it) or an HP8924C from Amtronix (new CRT, refurbished, calibrated, 1 year warranty). Other than the size and weight differences between the units what unit is the best buy? my main job for it is repeater and duplexer tuning, thank you all for your respected opinions and responses.

There are lots of things to consider, least of which is price and your budget. I haven't used the R2600 extensively, but I have used HP8920s a great deal and found them to be better quality and better display than the R2600. The tracking generator on the 8920 was better than most service monitors I've used, more accurate and better detail. I generally didn't use a service monitor for doing filter work; depending upon your budget, you might want to consider a lower cost service monitor for the radio work and a network analyzer for filter work. Even the lower end units like the HP 8711 (or 8712/13) do a much better job than any service monitor I've used when working with filters. The 8920 came close in accuarcy and display resolution to an 8713, but the network analyzer will allow you to view transmission and return loss at the same time (S21 and S11), have multiple markers, more accurate and a much better display (I'm not aware of any service monitor that measures return loss...). My 2 cents for what it's worth.....

Another 2cents on this topic:Keep in mind that a 2600A is going to be around 20 years old. There are many still in service, but most parts are no longer available, especially the CRT. A few board members have experienced age-related failures (capacitor cancer) in early model 2600s, that if not repaired in time can be fatal. You'd probably have to replace the memory battery anyway unless it was well maintained. No calibration + no warranty * old machine = probably a bad choice.Now, if it works 100% and you can get it really cheap it may be worth the risk. But if you plan on tuning cavities and duplexers, a good, fully functional tracking generator and spectrum analyzer are essential.

I have had 4 service monitors over the years, with the worst, being the IFR FM/AM 1000, which suffered from pass transistor failure, and the others have been the IFR 1500 and the IFR 7550(best).I currently have an R2001D/HS and the HP8924-C, which is a Cadillac compared to the R2600, and is standard with a good tracking generator, RF/AF analyzer, Encode and decode, O-Scope, and of course, CDMA testing included.

Like IFR(AeroFlex) and the Motorola (General Dynamics) R2600 series have an optional track gen. Whereas the HP 8924-C has this as a standard complement, and not an option, which is a need, and should never be an option for filter work.Even missing an operator's manual, the HP unit is easy to navigate, and make fully operational for most people's needs.You can program the 'K' buttons for direct access to the spectrum analyzer, RF generator, or any function you use the most.You can also store and recall specific settings using the front panel buttons.The biggest issue I have, is that the units come standard with a very LOW POWER input attenuator...Bad choice for accidental keying into the I/O port!3 watts is NOT much power, so act accordingly, or buy the higher wattage version.-C is HEAVY!

The manual is far more specific for CDMA testing, with radio test and measurement being secondary. I do like having the ability to test LTR and EDACS radio systems though, and the HP8924-C has these radio platforms as a standard offering.

When combines with an SWR bridge, testing and filter tuning is a breeze. All controls are simple to navigate, and the screens are identical for the most part, and the layout of the nav screens are simple to use and indicates all the necessary functions within that screen/mode.

I was able to reconfigure an old Decibel duplexer for use as a comb filter, by changing the interconnecting cables, using the 8924-C's track-Gen feature, as well as my eagle SWR bridge, I was able to get all 6 cavities to a notch depth of -63 dBm, which is far better than you can obtain using this duplexer as is.The 4607 duplexer was designed for the low end (430 mHz.) split, and this is the range I tuned it in. I was able to obtain a clean notch, and pretty 'deep' as well. I am happy I bought the HP, it's already made many chores far simpler!

If you are using this on the bench than the 8924C without any doubt is the far better choice. ( but I do have an HP bias since I have worked there over thirty years ...not with the Agilent side though )If its mostly portable/ field work than the 2600A may be a better fit given its weight and power options. ( battery and DC capable )Believe General Dynamics will still support the 2600 early units but that can be pricey depending on the failureThe basic 2600 design from an RF perspective does not appear to have changed much through the latest version but the processor, firmware and display have been updated/expanded along the way to support the current radio technology .I have repaired the 2600 CRT units ...mostly flybacks and caps etc and re-capped the surface mount 25 uF Caps that will leak eventually ( these are actually more of an issue on later C vintages than the earlier units ..manufacturing defect on the caps of a certain vintage I suspect ).The 8924C's have only one minor power supply issue but the rest is the typical HP built like a tank, CRT' modules have failed but the module and CRT are common across a number of HP product and have good availability today.Both the 2600 and 8924C are external video monitor capable ...usually requires and adapter for VGA monitors

The single greatest feature of the 8924C IMHO is the autotune feature on the transmitter test. Key up a radio and it automatically tunes to the carrier frequency. Makes transmitter alignments an absolute breeze.

I had an R2660 (the iDEN version of the R2600) and sold it off for an HP8921. The interface sucked and the 5MHz sawtooth pattern on the tracking generator (which was normal per Motorola and didn't go away with a full calibration) was horrible.

The 892x series are great monitors. The only problem with the 8924 is that it's a bench queen. It needs to live on a shelf, unless you enjoy hernias. If you want something that's more field-ready, look at an 8921 (make sure it has the 60 watt power option, or plan to install an upgrade kit).

escomm wrote:The single greatest feature of the 8924C IMHO is the autotune feature on the transmitter test. Key up a radio and it automatically tunes to the carrier frequency. Makes transmitter alignments an absolute breeze.

I wish I had the 60 watt option, but have the low ball variety, 3 Watt version.Transmitter testing is limited to my power attenuators on hand *sigh*

escomm wrote:The single greatest feature of the 8924C IMHO is the autotune feature on the transmitter test. Key up a radio and it automatically tunes to the carrier frequency. Makes transmitter alignments an absolute breeze.

I wish I had the 60 watt option, but have the low ball variety, 3 Watt version.Transmitter testing is limited to my power attenuators on hand *sigh*

Upgrade it. All you need to do is swap the attenuators and flash the thing. Amtronix and the like have parts.

Just use a high power external attenuator when needed. The 892X series allows you to configure external gain or loss by port to directly adjust the measured levels in and out of the unit.This way you get to keep the low power -10dbm measurements and easily get to high power when needed. For 5 Watt portables just go straight in.The attenuators are on ebay and range in price but I use a small 20db 25 watt unit that I picked up for around $30.

The nice thing is that you can use the 8924C to verify the exact loss at frequency and use that for the offset if you are going for an exact measurement or the attenuator used is not that flat.

I have power attenuators in stock, from 3dB to 50dB.And I am familiar with the input attenuator levels for the TX testing. I prefer having the direct ability, above the attenuator version.That leaves too many dongles on the bench for my tastes, but I see what you mean.

8924C, definitely. Others have pointed out the main reasons but I will add that I have been using an 8924C for about 2 years now and I just haven't seen much else which comes close in terms of performance & versatility for the money. These were $30k lab grade instruments when new and it shows. The 8924C is in essence a fully optioned 8920A. For analog testing procedures, refer to the 8920 series application guide - virtually all of the information will apply to the 8924C as well.

If you don't need field portability but still want to move your 8924C around the shop, you can put it on a cart. I used a modified old Tektronics 500 series scope cart.

I see this thread is about 7 months old now.....so which one did you get?

Since this is back to life I'll add my thoughts. For transmitter work I prefer the HP8901B with the 11722A. I leave it connected to a 200W Bird 30 dB attenuator so mW = W, dBm = dBW. Autotune frequency, power, modulation with ovened frequency standard. Even does P25, the proper settings are spec'd by Moto in the older service manuals. Very much a desk queen but cheap these days.

For duplexers you can't beat a dedicated network analyser as Mr Pink mentioned. I use the 8711 scaler version of the 8713 as I don't need vector measurements.

I see the HP/Agilent/Keysight (or whatever they call themselves this week) Fieldfox is becoming popular for field use.

escomm wrote:The single greatest feature of the 8924C IMHO is the autotune feature on the transmitter test. Key up a radio and it automatically tunes to the carrier frequency. Makes transmitter alignments an absolute breeze.

I wish I had the 60 watt option, but have the low ball variety, 3 Watt version.Transmitter testing is limited to my power attenuators on hand *sigh*

Upgrade it. All you need to do is swap the attenuators and flash the thing. Amtronix and the like have parts.

I purchased a low power 8920 and Amtronix provided an upgrade to 60W for $210. It included the use of a calibration card and a 60W label for the front panel. I had to return the cal card on my dime.

By the way, if you do not mind a big power attenuator sticking out of the instrument you can go to the setup screen and add the atten value and the monitor will compensate for it automatically. I briefly used a 25W 20DB pad until I emailed Amtronix.

Just to update my post. I finally purchased the HP8924C 100 watt unit from Amtronix, I can tell you though that it is too heavy and I am currently planning on buying a Motorola R2600 also, I know, I know but my back will thank me specially when going up to the repeater sites. HP8924C beautiful machine but a true bench queen. Thanks to all that replied.

Why buy a 2600? There are tons of 8920s and 8921s out there, and they have the exact same interface as your 8924. Leave the 24 on the bench, carry the 20/21 with you, and only have one system to learn.

Well I want to say thanks to everyone that participated in this thread. I've been reading up and trying to find a used service monitor for my limited budget. I'm having trouble finding one with the 60/100 watt option that's in good shape for the price.

What about the hp 8924e? I've seen a couple of those come up.

Also I guess if I don't find one for the right price I guess I can buy the 3w version and just use an antennuator for higher wattage input. What if I buy the 60/100w hardware and install it myself. Would that require it to be sent back and calibrated?

Hello to all. I know it has been a long time since I replied to this thread but here it goes: Like I mentioned on 5/7/2014 I did purchase an 8924C with the 100 watt option from Amtronix along with the return loss bridge from them, this is my main rig for EVERYTHING and I love it. Learning curve is a little steep though but when you get it, everything clicks into place, I have even managed to redo duplexers that were supposed to be "fine" and now they are a true beauty. I have also managed to carry it to some repeater sites using a big Pelican 1600 case ($350 on EBay) and it really does the trick that way, but still I think it belongs on the bench. However, here is the true update: I got yesterday in the mail a very very clean Motorola R2660C for "dirt cheap" money that I could not pass it up, so finally I do have both units to do a true comparison and from what I have briefly seen on the Motorola the HP units are far more accurate, the Motorola is just an easy to use "box" that I can lug around (I got the carry case also include). I know some of you suggested to buy another 8920 but man they are still kind of pricey even on EBay, and so my budget does not allow it at this time. Although that will be my next purchase I am sure. I will keep playing with the R2660C and update. Again thank you all for the replies, opinions and interest. Best regards and Happy Holidays.

After using, and liking the 8901B I also upgraded to an 8924C - I found one at the right price and the newer interface, extra features, and faster measurement speed make it a joy to use. Much prefer it to the 8901B which is getting a bit long in the tooth.

I was actually considering an 8901 for my home bench. At the shack our club has every piece of test gear imaginable, but it's not always accessible and I'd like to be able to work on radios without dragging them up three flights of stairs.

I figure that since I don't need much more than frequency and deviation an 8901, an RF sampler, and a dummy load would be all I'd really need for a basic test set.

Would you still recommend the 8901 for someone who doesn't have a large amount of cash to spend on test gear?

Absolutely. Aside from the measurement speed, which only suffers when measuring frequency down to 1Hz for example, it works fine. As ASTRO Spectra said, it's perfect for aligning P25 gear, and it can do the majority of alignment on DMR as well. The ASTRO and ASTRO25 service manuals even recommend the 8901A/B in addition to the Motorola/GD R2xxx series.

I keep mine plugged into the wall all the time to keep the ovened oscillator warm and at temp, and it helps keep the unit dry as well (thanks for the tips ASTRO Spectra)

About the only thing you'll need in addition to the 8901B is an attenuator, as it can only handle 1 watt max input. I also have a 10MHz GPSDO reference that I use as well, but it's overkill for most applications.